As a wearable electrical apparatus worn on a user's body when used, an input interface worn on a finger is known.
For example, one conventional interface (for example, patent document 1) has a ring-shaped base worn on a user's forefinger, a circumferentially long touch pad for vertical scrolling and a tact switch for horizontal scrolling adjacent to the touch pad. In this input interface, the touch pad and the tact switch are operated by the thumb adjacent to the forefinger, on which the base is worn.
Another conventional input interface (for example, patent document 2) is configured to be capable of detecting keying operation on an arbitrary supporting body, such as a desk. This input interface analyzes timing, with which a user taps the supporting body at his/her finger tips to determine input information based on a detection signal from a detector, such as impact sensor, sound sensor, acceleration sensor, myoelectric sensor, or the like.    Patent document 1: JP 2006-302204A    Patent document 2: JP H7-121294A
However, according to the input interface of patent document 1, for example, it is required to operate the small-sized touch pad and tact switch fit on the forefinger by the thumb, and this degrades the operability of the input interface. Further, it is required to finely and accurately move the thumb.
The input interface according to patent document 2 is so designed as to determine input information by detecting the action of tapping the supporting body by a user. Therefore, although it can be utilized in keyboard entry and the like, in which tapping operation is mainly performed, it cannot detect any other operation than tapping, such as long-time pressing. As a result, its input pattern is limited and it is unsuitable for other applications.